Obviously if someone is vegeterian then its understandable they don't to eat any meat.
We want cheap food. Horse meat is far cheaper than beef. Rabbit meat is cheap as well.
Surely the important thing is to make sure that animals have a humane existance before slaughter. I feel its silly to get overly sentimental about eating horses or rabbits, but not care a damn about the welfare of cattle, sheep , chicken or pigs. The horses that got eaten probably had a better life than many battery chickens.
I think the issue with horsemeat lasanga is deception and labelling rather than the fact that some horse meat has got eaten. If the meat had been honestly labelled then it would have been a good source of protein for a cash strapped family.
I would rather eat properly tracked horsemeat than some really dubious cuts of beef. (Ie. remember mad cow disease.)